An image from NASA TV shows the troubling gouge on Endeavour's underside today.

An image from NASA TV shows the troubling gouge on Endeavour's underside today.

Photo: Associated Press

Image 2 of 4

This image from NASA TV shows a white streak, at the center of the frame, coming off of the shuttle 58 seconds after liftoff. Engineers theorized that it was ice, but have concluded that a foam chunk is to blame for scraping the heat shield. less

This image from NASA TV shows a white streak, at the center of the frame, coming off of the shuttle 58 seconds after liftoff. Engineers theorized that it was ice, but have concluded that a foam chunk is to ... more

Photo: AP

Image 3 of 4

This image made available Friday by NASA shows a white gouge, bottom left, and scrapes against the black tiles on the underside of space shuttle Endeavour.

This image made available Friday by NASA shows a white gouge, bottom left, and scrapes against the black tiles on the underside of space shuttle Endeavour.

The problem, which may require repair by some of the shuttle's astronauts, was discovered soon after the ship docked with the international space station.

A 3 by 3-inch gouge was found in soft protective shielding under the shuttle's right wing in closeup photos taken by the station's two Russian cosmonauts as Endeavour approached for the linkup this afternoon.

NASA plans to take a closer look Sunday, when shuttle astronauts wave cameras and lasers on the tip of Endeavour's robot arm across the gouge to measure its depth.

Just more than three hours into the spacewalk, NASA's main command-and-control computer aboard the space station mysteriously shut down. The backup automatically kicked in, and the third computer went from standby to backup. Mission Control said the problem did not affect the spacewalk or the health of the station.

Endeavour's launch Wednesday night was tracked by cameras as well as radar, revealing what appeared to be ice dislodging from the spacecraft and spraying the damaged region, said John Shannon , who chairs NASA's mission management team.

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NASA rediscovered the vulnerability of the shuttle's heat shielding in 2003, when the shuttle Columbia disintegrated as it descended to Earth. The cause of the breakup that killed seven astronauts was traced to an undiscovered hole in the armoring of the left wing caused by a blow from breakaway foam fuel tank insulation during liftoff.

Also Friday, the space agency said an orbiting fragment from a Delta rocket launched from California on Aug. 9, 1975 passed within 1.3 miles of Endeavour and its crew of seven astronauts about 90 minutes after they lifted off.

The space agency relies on military radar tracking of thousands of pieces of manmade space debris to determine whether the material poses a collision risk. Though the fragment passed outside the safety zone that NASA tries to maintain around the shuttle, it was closer than anticipated, said NASA's Matt Abbott , the shuttle's lead flight director for the mission.

The shuttle's seven astronauts, including former teacher Barbara Morgan, were informed of both developments today.

"Thanks for the update," Kelly told Mission Control, when told of the gouge by Mission Control. "Good enough."

The Columbia tragedy prompted the space agency to make thorough inspections of the shielding a regular part of each mission, scheduling the surveys in the days following liftoff and just prior to landing.

It was too soon to know whether Endeavour's damage will require repairs by the astronauts with materials aboard the shuttle, Shannon said Friday.

The damage is in a region of the shuttle where temperatures build to 1,500 to 2,300 degrees Fahrenheit as the shuttle slices through the Earth's atmosphere during a long glide to the runway.

Endeavour carries three repair options developed in Columbia's aftermath.

One is an undercoating fluid of carbon and silicon that astronauts can dab on the damage to fend off heat. Another is a plate-like overlay made from a similar heat-resistant material that can be bolted over the damage. A third option is a caulk-like substance that can be troweled across the damage.

Each of the techniques has been tested on previous shuttle missions and subjected to conditions that simulate the shuttle's re-entry in NASA labs and wind tunnels.

In the worst case, the space station could serve as a refuge for the Endeavour crew until NASA could mount a rescue. The station has enough supplies to sustain all 10 astronauts and cosmonauts for 68 days.

The shuttle crew docked at the space station with plans for a seven to 10 day stay.